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Structure of the atom
Year | Scientist | Theory |
400 B.C | Democritus | There were 6 points to his theory of atoms.-All matter is composed of atoms, which are bits of matter too small to beseen. These atoms cannot be further split into smaller portions.-There is a void, which is empty space between atoms.-Atoms are completely solid-Atoms are homogeneous, with no internal structure.-Atomsare different in: their sizes, their shapes, and their weights.-Atoms are the building blocks of life |
1803 | John Dalton |  His theory was made up of five important points.-Elements are composed oftiny particles called atoms.-All atoms of a given element are identical.-The atoms of a given element are different from those of any other element; the atoms of different elements can bedistinguished from one another by their respective relative weights.-Atoms of one element can combine with atoms of other elements to form chemical compounds; a given compound always has the same relative numbersof types of atoms.-Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together. |
1897 |J.J. Thomson | -Cathode rays bent away from a negatively charged plate so he concluded that these rays are made of negatively charged particles (electrons) -Electrons were found in all atoms and areover a thousand times smaller than protons.-Negatively charged electrons were fixed in a sphere of positive charge so the charges were balance. Plum Pudding Model-The bits of "plum" were the electronswhich were floating around in a "pudding" of positive charge to match that of the electrons and make an electrically neutral atom. |
1898 | Rutherford | -Atoms have a nucleus which is very small anddense, containing the positive charge and most of the atom's mass.-Electrons are attracted to the nucleus, but stay far outside it.-The electrons revolve around the nucleus in different circular...